CONH

CONH is a shorthand notation used in chemistry to denote the amide linkage -C(=O)NH-, a key structural motif in organic and biochemistry. This fragment connects a carbonyl carbon to a nitrogen atom and is central to the class of compounds known as amides.

Structure and bonding

The amide linkage features resonance between the lone pair on nitrogen and the carbonyl group, giving partial double-bond character to the C–N bond and planarity around the linkage. This resonance stabilizes the amide, reduces the reactivity of the carbonyl toward nucleophiles, and restricts rotation about the C–N axis. The NH portion also serves as a hydrogen bond donor, while the carbonyl oxygen is a hydrogen bond acceptor, influencing the conformation and interactions of amide-containing molecules.

Occurrence and formation

Amide linkages are formed by condensation between a carboxyl derivative and an amine, with the release of water. In biology, the most prominent example is the peptide bond that links amino acids in proteins and peptides, creating lengthy polypeptide chains with repeating CONH units. Amide linkages also form the backbone of many synthetic polymers known as polyamides, such as the nylon family.

Properties and applications

Amides, and thereby the CONH motif, are relatively stable under ordinary conditions and resist hydrolysis compared with esters, often requiring acids, bases, or enzymatic catalysis to cleave the bond. The CONH group contributes to the physical properties of materials (strength, rigidity, hydrogen-bonding networks) and plays a central role in biochemistry, pharmaceutical design, and polymer chemistry.

See also

Amide, peptide bond, carbamoyl group, polyamide.